The Impact of Weather Conditions on Response of Sorghum Genotypes to Anthracnose (Colletotrichum sublineola) Infection

Rainfall is a major climatic factor influencing anthracnose development. In this study, 68 sorghum accessions were evaluated for anthracnose resistance under dry and wet growing conditions at the Texas A&M Agricultural Experiment Station, near College Station, Texas. Accessions, planted in a randomized complete block design with three replications, were inoculated with a mixture of Colletotrichum sublineola isolates 30 days after planting. Under dry growing conditions, three accessions showed a susceptible response across replications, whereas 41 accessions exhibited susceptibility under wet growing conditions. Also, 15 accessions that showed variation in susceptibility across replications under dry conditions were rated as susceptible across replications under wet growing conditions. Nineteen accessions consistently showed a resistant response under both dry and wet growing conditions. There was no significant correlation between weather variables and anthracnose development during the dry growing season, suggesting that climatic conditions were unfavorable for disease development. In contrast, there was a significant positive correlation between total rainfall and anthracnose infection and moderately significant relationships between number of days with rain and minimum relative humidity, with anthracnose infection during wet growing conditions. These results indicate that frequency and cumulative rainfall, as well as relative humidity are critical factors for disease development.